Smoothing-technology-based physical layer blind authentication method and system for time-varying fading channel

ABSTRACT

Provided is a physical layer blind authentication method for a time-varying fading channel based on a smoothing technique. The method includes that: a transmitter transmits a carrier signal to a wireless channel, the carrier signal includes an authentication signal, a pilot signal and an information signal, and the wireless channel is the time-varying fading channel; a receiver receives the carrier signal, and performs BKIC processing and differential signal processing on the carrier signal to obtain a target authentication signal, performs the differential signal processing on the reference signal to obtain a reference authentication signal, and calculates a correlation between the target authentication signal and the reference authentication signal to obtain a test statistic; and compares the test statistic with a prescribed threshold to determine whether the carrier signal is capable of passing authentication.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a national stage application, filed under 37 U.S.C. 371, ofInternational Patent application No. PCT/CN2017/116027, filed on Dec.13, 2017.

TECHNICAL FIELD

The present disclosure relates to the field of wireless communicationtechnologies, and in particular to a physical layer blind authenticationmethod and system for a time-varying fading channel based on a smoothingtechnique.

BACKGROUND

At present, three main physical layer authentication technologies exist.The first authentication technology is the Spread SpectrumAuthentication method (Auth-SS). The basic idea is to use thetraditional direct-sequence spread spectrum or frequency hoppingtechnology. Since different pulses use different frequencies, thistechnology requires a certain amount of bandwidth to achieveauthentication. In addition, a key limitation of the Auth-SS technologyis that only users who understand prior knowledge of the spread spectrumtechnology are involved in the communication. Therefore, the scope ofapplication of this technology is relatively narrow.

The second authentication technology is based on the Authentication withTime Division Multiplexing (Auth-TDM). The basic idea is that thetransmitter periodically sends information signals and authenticationsignals alternately. After receiving a signal, the receiver directlyextracts the desired authentication information to implementauthentication of the signal. The Auth-TDM is an authenticationtechnology proposed in the early development of wireless communication.The advantage is that it is easy to operate, and that authenticationsignals and information do not need to be pre-processed (encryption maybe performed for security reasons) before signals are transmitted. Theauthentication signal is transmitted independently of the informationsignal, so the authentication signal needs to occupy a certain amount ofbandwidth. With the increasing amount of wireless information, furtherimprovement of information privacy for users and the continuousenhancement of attack technologies of the enemy, the security of thisauthentication technology is greatly challenged and cannot meet therequirements of users.

The third authentication technology is the Authentication withSuperimposition (Auth-SUP). The basic idea is to superimpose theauthentication signal on the information signal (the superimpositionmanner may be arbitrary and is determined by the key), and then thetransmitter simultaneously transmits the authentication signal and theinformation signal, and after the receiver receives the signals, theauthentication signal in the superimposed signals is extracted by usingthe key to achieve the purpose of signal authentication.

Compared with the early Auth-TDM technology, in the Auth-SUPauthentication technology, the authentication signal and the informationsignal need to be processed before signal transmission, a certain signalprocessing capacity of the transmitter is required, which is morecomplicated to achieve than the Auth-TDM technology, and theauthentication signal and the information signal are simultaneouslysent, so that extra bandwidth is not occupied. At this time, since theauthentication signal is superimposed in the information signal, thereceiver needs to extract the information after receiving the signal, sothe signal processing difficulty is higher than that of the Auth-TDMtechnology, but the concealment of the authentication information ishigher than that of the Auth-TDM. In addition, since the authenticationsignal plays a role of noise for the extraction of the informationsignal, the signal-to-noise ratio (SNR) of the receiver iscorrespondingly reduced, which adversely affects the extraction of theinformation signal.

In the existing Auth-TDM and Auth-SUP authentication technologies,another pilot signal is further transmitted in addition to theinformation signal and the authentication signal since for the twoauthentication technologies, the receiver needs to estimate the channelparameters and recover the symbols after receiving the signals and thenextracts the authentication signal, so that a certain signal processingcapability of the receiver is also required. In some specific cases,these signal processing technologies may not be feasible and may easilycause estimation errors in the channel parameter estimation and symbolrecovery processes, which may adversely affect the final extraction ofthe authentication signal.

In addition, the Auth-TDM, the Auth-SS, and the Auth-SUP expose the factthat authentication information is included. Auth-SS and Auth-TDMtechnologies are more likely to attract the attention of other users inthe scenario, especially hostile users, compared with conventionalsignals that do not include authentication information. The hostile useranalyzes, counterfeits or tampers with the signal, and the legitimatereceiver cannot authenticate the expected signal. Relatively speaking,the concealment of the Auth-SUP authentication technology issignificantly higher than that of Auth-SS and Auth-TDM. However, thissuperiority is based on the premise that the computing power of thehostile user is limited. Once the computing power of the hostile user isincreased, it is also possible for the hostile user to extract or evendestroy the authentication information.

It must be mentioned that the existing Auth-SS technology and Auth-SUPtechnology have severe performance degradation in the time-varyingfading channel scenario. The reality is that as the number of wirelesscommunication users continues to increase, the communication environmentwill become more complex and the possibility of interference willincrease. As the number of urban communication users increases and thecity continues to develop, the simple time invariant fading channel isnot sufficient to characterize the current communication environment.Therefore, it is necessary to consider the wireless communicationphysical layer authentication technology based on the time-varyingfading channel to improve the security of wireless communication andmeet the communication security requirements of users.

SUMMARY

In view of the above, the present disclosure aims to provide a physicallayer blind authentication method and system for a time-varying fadingchannel based on a smoothing technique. In the method and system, extrasignal bandwidth is not needed, the authentication signal does notbecome noise affecting the extraction of an information signal in acarrier signal, and the statistical characteristic of the noise at thereceiver is not affected.

Thus, in a first aspect of the present disclosure, a physical layerblind authentication method for a time-varying fading channel based on asmoothing technique is provided, which is a physical layerauthentication method for wireless communication of a wirelesscommunication system having a transmitter and a receiver. The methodincludes: transmitting, by the transmitter, a carrier signal to awireless channel, where the carrier signal includes an authenticationsignal, a pilot signal, and an information signal, the authenticationsignal is superimposed on the pilot signal, and the wireless channel isthe time-varying fading channel; receiving, by the receiver, the carriersignal, and performing blind known interference cancellation (BKIC)processing and differential signal processing on the carrier signal toobtain a target authentication signal, where in the BKIC processing, thepilot signal is cancelled through the smoothing technique by usingadjacent symbols; obtaining, by the receiver, a reference signal basedon a key and the pilot signal, performing the differential signalprocessing on the reference signal to obtain a reference authenticationsignal, and calculating a correlation between the target authenticationsignal and the reference authentication signal to obtain a teststatistic; and comparing the test statistic with a prescribed thresholdto determine whether the carrier signal is capable of passingauthentication.

In the present disclosure, the authentication signal is superimposed onthe pilot signal. Thus, the Signal to Interference plus Noise Ratio atthe receiver may not be affected. In the BKIC processing, the pilotsignal is cancelled through the smoothing technique by using theadjacent signals. In this case, the pilot signal can be cancelledwithout channel estimation.

In the physical layer blind authentication method provided in the firstaspect of the present disclosure, the carrier signal is transmitted inblocks in a form of data blocks to facilitate operation of data.

In the physical layer blind authentication method provided in the firstaspect of the present disclosure, in each carrier signal block, a sum ofa length of a pilot signal and a length of an information signal isequal to a length of the each carrier signal block.

In addition, in the physical layer blind authentication method providedin the first aspect of the present disclosure, the reference signal isobtained based on the key and the pilot signal by using a hash matrix.Thus, the reference signal is processed to obtain the referenceauthentication signal and it can be determined whether the targetauthentication signal passes the authentication according to thecorrelation between the reference authentication signal and the targetauthentication signal.

In the physical layer blind authentication method provided in the firstaspect of the present disclosure, if the test statistic is not less thanthe prescribed threshold, the carrier signal passes the authentication.

In the physical layer blind authentication method provided in the firstaspect of the present disclosure, the prescribed threshold is obtainedbased on a statistical characteristic of the pilot signal and a presetupper limit of a false alarm probability.

In a second aspect of the present disclosure, a physical layer blindauthentication device for a time-varying fading channel based on asmoothing technique is provided. The device includes a processor and amemory. The processor is configured to execute a computer program storedin the memory to implement any physical layer blind authenticationmethod described above.

In a third aspect of the present disclosure, a computer readable storagemedium is provided and is configured to store at least one instructionwhich, when executed by a processor, implements any physical layer blindauthentication method described above.

In a fourth aspect of the present disclosure, a physical layer blindauthentication system for a time-varying fading channel based on asmoothing technique is provided. The system includes a transmittingdevice and a receiving device. The transmitting device is configured totransmit a carrier signal to a wireless channel, where the carriersignal includes an authentication signal, a pilot signal and aninformation signal, the authentication signal is superimposed on thepilot signal, and the wireless channel is the time-varying fadingchannel. The receiving device comprises: a first processing module, asecond processing module, and a determining module. The first processingmodule is configured to receive the carrier signal and perform blindknown interference cancellation (BKIC) processing and differentialsignal processing on the carrier signal to obtain a targetauthentication signal, where in the BKIC processing, the pilot signal iscancelled through the smoothing technique by using adjacent symbols. Thesecond processing module is configured to obtain a reference signalbased on a key and the pilot signal, perform the differential signalprocessing on the reference signal to obtain a reference authenticationsignal, and calculate a correlation between the target authenticationsignal and the reference authentication signal to obtain a teststatistic. The determining module is configured to compare the teststatistic with a prescribed threshold to determine whether the carriersignal is capable of passing authentication.

In the present disclosure, the transmitting device of the physical layerblind authentication system superimposes the authentication signal onthe pilot signal. Thus, no extra transmitting bandwidth resource isoccupied. The receiving device of the physical layer blindauthentication system performs the BKIC processing in which the pilotsignal is cancelled through the smoothing technique by using theadjacent symbols. In this case, the receiving device can cancel thepilot signal without channel estimation.

In the physical layer blind authentication system provided in the fourthaspect of the present disclosure, the second processing module isconfigured to obtain the reference signal based on the key and the pilotsignal using a hash matrix. Thus, the reference signal is processed toobtain the reference authentication signal and it can be determinedwhether the target authentication signal passes the authenticationaccording to the correlation between the reference authentication signaland the target authentication signal.

In the physical layer blind authentication system provided in the fourthaspect of the present disclosure, in the determining module, theprescribed threshold is obtained based on a statistical characteristicof the pilot signal and a preset upper limit of a false alarmprobability.

Compared with the existing art, the embodiments of the presentdisclosure have the following beneficial effects.

Compared with the existing Auth-SS, Auth-SUP, and Auth-TDM, the presentdisclosure requires no extra signal bandwidth to implementauthentication of the physical layer of the wireless communication, theauthentication signal does not become noise affecting extraction of thereceiving signal, and the statistical characteristics of noise at thereceiver is not affected. The blind authentication technology providedby the present disclosure deals with a time-varying fading channel, andis more applicable to complicated and variable wireless communicationenvironment in the actual communication scenarios. In addition, since inthe present disclosure, the authentication signal is superimposed on thepilot signal, if the entire signal obtained by superimposing theauthentication signal and the pilot is used as a pilot signal, theaccuracy of channel estimation can further be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram illustrating signal transmission of aphysical layer blind authentication method according to an embodiment ofthe present disclosure;

FIG. 2 is a schematic flowchart of a physical layer blind authenticationmethod according to an embodiment of the present disclosure;

FIG. 3 is a schematic structural diagram of a signal transmitted by atransmitter in a physical layer blind authentication method according toan embodiment of the present disclosure;

FIG. 4 is a schematic flowchart of a process of blind known interferencecancellation (BKIC) processing at a receiver in a physical layer blindauthentication method according to an embodiment of the presentdisclosure;

FIG. 5 is a schematic diagram illustrating signal processing modules ofa transmitter in a physical layer blind authentication system accordingto an embodiment of the present disclosure;

FIG. 6 is a schematic diagram illustrating signal processing modules ofa receiver in a physical layer blind authentication system according toan embodiment of the present disclosure; and

FIG. 7 is a schematic structural diagram of a physical layer blindauthentication device according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The preferred embodiments of the present disclosure will be described indetail below with reference to the drawings. In the followingdescription, the same components are denoted by the same referencenumerals, and the description thereof will not be repeated. In addition,the drawings are merely schematic and the ratio of the dimensions of thecomponents to each other or the shapes of the components and the likemay be different from the actual ones.

It should be noted that the terms “first”, “second”, “third”, “fourth”and the like in the description, claims and above drawings of thepresent disclosure are used to distinguish between different objects,and are not intended to describe a specific order. Furthermore, theterms “comprises” and “comprising” and any variant thereof are intendedto cover a non-exclusive inclusion. For example, a process, method,system, product, or device that includes a series of steps or units isnot limited to the listed steps or units, but optionally also includessteps or units not listed, or other steps or units optionally inherentto these processes, methods, products or devices.

The embodiments disclose a physical layer blind authentication method,device and system for a time-varying fading channel based on a smoothingtechnique, which is a physical layer authentication method, device andsystem for wireless communication of a wireless communication systemhaving a transmitter and a receiver. That is, the embodiments disclose aphysical layer blind authentication method, device, and system for awireless communication time-varying fading channel based on a smoothingtechnique. The physical layer authentication can be performed moreaccurately. The details are described below in conjunction with thedrawings.

FIG. 1 is a schematic diagram illustrating signal transmission of aphysical layer blind authentication method according to an embodiment ofthe present disclosure.

In the present embodiment, as shown in FIG. 1, the physical layer blindauthentication method of the wireless communication time-varying fadingchannel based on the smoothing technique is based on a general signaltransmission model. In this signal transmission model, four users areincluded, the sending party (transmitter) is a legitimate sending party,the transmitter transmits a signal to the legitimate receiving party(the receiver), and the other two receiving parties are a listening userand a hostile user in the system. Once the hostile user finds thatauthentication information may exist in the signal sent by thetransmitter, the hostile user will analyze the signal, and attempt toextract, destroy, or even tamper with the authentication information.However, the embodiment is not limited thereto, two or more transmittersmay exist, two or more legitimate receiving parties may exist, and twoor more listening users and two or more hostile users may exist.

In the present embodiment, it is assumed that the transmitter and thereceiver jointly have a key for authentication, so that the receiver canuse the key to extract authentication information from the signaltransmitted by the transmitter. The authentication signal includesauthentication information. In the present embodiment, the carriersignal includes an authentication signal, and the conventional signaldoes not include an authentication signal. The listening user knowsnothing about the authentication method. Although the listening user canaccept and recover the signal sent by the transmitter, the listeninguser does not analyze the signal in depth and does not affect theauthentication process. The hostile user can detect the existence of theauthentication signal by analyzing the characteristics of the signal,and intends to destroy the authentication signal.

In the present embodiment, the transmitter in the above signal model mayinclude a base station or a user equipment. The base station (e.g., anaccess point) may refer to a device in an access network thatcommunicates with a wireless terminal over one or more sectors over anair interface. The base station may be used to convert the received airframe and the IP packet to each other and act as a router between thewireless terminal and the rest of the access network, where the rest ofthe access network may include an Internet Protocol (IP) network. Thebase station may also coordinate attribute management of the airinterface. For example, the base station may be a Base TransceiverStation (BTS) in Global System for Mobile Communication (GSM) or CodeDivision Multiple Access (CDMA), or may be a base station (NodeB) inwideband CDMA (WCDMA), or may be an evolutional Node B (NodeB or eNB ore-NodeB) in Long-Term Evolution (LTE), which is not limited in thepresent embodiment.

The user equipment may include, but is not limited to, a smart phone, anotebook computer, a personal computer (PC), a personal digitalassistant (PDA), a mobile Internet device (MID), a wearable device (suchas a smart watch, a smart bracelet and smart glasses) and various typesof electronic devices, where the operating system of the user equipmentmay include, but is not limited to, an Android operating system, an IOSoperating system, a Symbian operating system, a BlackBerry operatingsystem, the Windows Phone 8 operating system and so on, which is notlimited in the present embodiment.

In the present embodiment, the transmitter in the above signal modeltransmits a signal to the receiver through the wireless channel, wherethe receiver may include the base station. The base station (e.g., anaccess point) may refer to a device in an access network thatcommunicates with a wireless terminal over one or more sectors over anair interface. The base station may be used to convert the received airframe and the IP packet to each other and act as a router between thewireless terminal and the rest of the access network, where the rest ofthe access network may include an Internet Protocol (IP) network. Thebase station may also coordinate attribute management of the airinterface. For example, the base station may be a Base TransceiverStation (BTS) in GSM or CDMA, or may be a base station (NodeB) in WCDMA,or may be an evolutional Node B (NodeB or eNB or e-NodeB) in LTE, whichis not limited in the present embodiment.

The receiver may further include a user equipment. The user equipmentmay include, but is not limited to, a smart phone, a notebook computer,a personal computer (PC), a personal digital assistant (PDA), a mobileInternet device (MID), a wearable device (such as a smart watch, a smartbracelet and smart glasses) and various types of electronic devices,where the operating system of the user equipment may include, but is notlimited to, an Android operating system, an IOS operating system, aSymbian operating system, a BlackBerry operating system, the WindowsPhone 8 operating system and so on, which is not limited in the presentembodiment.

The embodiments disclose a physical layer blind authentication methodfor a wireless communication time-varying fading channel based on asmoothing technique. FIG. 2 is a schematic flowchart of a physical layerblind authentication method according to an embodiment of the presentdisclosure. FIG. 3 is a schematic structural diagram of a signaltransmitted by a transmitter in a physical layer blind authenticationmethod according to an embodiment of the present disclosure.

In the present embodiment, the physical layer blind authenticationmethod of the wireless communication time-varying fading channel basedon the smoothing technique is a physical layer authentication method forwireless communication of the wireless communication system having thetransmitter and the receiver. Based on the signal transmission modeldescribed above, as shown in FIG. 2, the transmitter transmits a carriersignal to the wireless channel. The carrier signal includes anauthentication signal, a pilot signal, and an information signal. Theauthentication signal is superimposed on the pilot signal. The wirelesschannel is the time-varying fading channel (step S101).

In step S101, as shown in FIG. 3, the carrier signal includes anauthentication signal, a pilot signal, and an information signal, andthe authentication signal is superimposed on the pilot signal. Thesignal length of the authentication signal is equal to the signal lengthof the pilot signal. Thus, the superimposition of the authenticationsignal onto the pilot signal avoids taking up extra signal bandwidth.

In the present embodiment, the information signal includes informationto be transmitted by the user at the transmitter. The carrier signaltransmitted by the transmitter is transmitted in blocks in the form ofdata blocks. Each of the carrier signal blocks includes a pilot portionand an information portion. The pilot portion includes an authenticationsignal and a pilot signal. The information portion includes aninformation signal. In addition, the carrier signal is transmitted inblocks in the form of data blocks, which facilitates manipulation of thedata.

In the present embodiment, the signal length of the authenticationsignal or the pilot signal is the first length, the signal length of theinformation signal is the second length, the length of each carriersignal block is the total length, and the sum of the signal length ofthe authentication signal or the pilot signal and the signal length ofthe information signal is equal to the length of each carrier signalblock, that is, the sum of the first length and the second length isequal to the total length.

In the present embodiment, the authentication signal is obtained throughthe pilot signal and the key, that is, the authentication signal isobtained through the pilot signal and the key using the hash matrix. Theobtained authentication signal is superimposed on the pilot signal, andthe pilot portion of each carrier signal block is obtained. The signalexpression of the pilot portion is as follows:m _(i)=ρ_(s) p _(i)+ρ_(t) t _(i)  (1)

In the above signal formula (1) of the pilot portion, ρ_(s) ² and ρ_(t)² are respectively the power allocation factors of the pilot informationand the authentication signal. Assuming that the authentication signaland the pilot signal are independent from each other, E{p_(i)^(H)t_(i)}=0 is obtained.

In the present embodiment, the signal of the pilot portion and theinformation signal of the information portion are combined to form eachcarrier signal block.

Further, in the present embodiment, the transmission channel of thecarrier signal is a wireless channel and is a time-varying fadingchannel. The expression of a carrier signal that has passed through thetime-varying fading channel is as follows:y _(iL+k) =h _(iL+k) x _(iL+k) +n _(iL+k)  (2)

In the present embodiment, the channel response h_(iL+k) of thetime-varying fading channel follows a complex Gaussian distribution witha mean of zero and a variance of σ_(h) ². In addition, dynamiccharacteristics of h_(iL+k) are characterized as a first-order GaussMarkov process, and the expression of the first-order Gauss Markovprocess is as follows:h _(iL+k) =ah _(iL+k−1)+ω_(iL+k)  (3)

In general, a∈[0,1] in formula (3) is a fading correlation coefficient,which is determined by the channel Doppler spread and the transmittingbandwidth. In particular, a small value of a indicates fast fading, anda large value of a indicates slow fading. In many types of scenarios,the value of a is available at the receiver. In the actual wirelesssystem scenario, the value of a ranges in a very small interval, forexample, a∈[0.9,1].

In the present embodiment, the physical layer blind authenticationmethod further includes that the receiver receives the carrier signal,and performs blind known interference cancellation (BKIC) processing anddifferential signal processing on the carrier signal to obtain a targetauthentication signal. In the BKIC processing, the pilot signal iscancelled through the smoothing technique using adjacent symbols (stepS102).

In the present embodiment, the receiver receives the carrier signal. Thecarrier signal includes a pilot portion and an information portion. Thephysical layer blind authentication method according to the presentembodiment is mainly used for processing the pilot portion of thecarrier signal at the receiver. The expression of the pilot portion ofthe carrier signal received at the receiver is as follows:y _(k) =h _(k)(ρ_(s) p _(k)+ρ_(t) t _(k))+n _(k) ,iL≤k≤iL+L ₁  (4)

In the present embodiment, the following processing for the carriersignal refers to the processing for the pilot portion of the carriersignal.

In step S102, the receiver receives the carrier signal and performs theblind known interference cancellation (BKIC) processing on the carriersignal to obtain a target signal. In the BKIC processing, the pilotsignal in the carrier signal is cancelled through the smoothingtechnique by using the adjacent symbols. Generally, the channelestimation is needed to cancel the pilot signal in the carrier signal.If the channel response cannot be effectively estimated, it is difficultto cancel the pilot signal in the carrier signal. The pilot signal canbe cancelled by using the blind known interference cancellation methodwithout the channel estimation.

In the present embodiment, the carrier signal received by the receivermay or may not include the authentication signal. That the carriersignal includes the authentication information is set as a firstcondition, and that the carrier signal does not include theauthentication signal is set as a second condition.

FIG. 4 is a schematic flowchart of a process of blind known interferencecancellation (BKIC) processing at the receiver in the physical layerblind authentication method according to an embodiment of the presentdisclosure.

In the present embodiment, as shown in FIG. 4, the BKIC processingincludes determining an expression of each symbol under differentconditions (step S401) and estimating the target signal using theexpression of the symbol (step S402).

In step S401, the expression of each symbol under different conditionsis determined.

Under the first condition, the expression of each symbol is as follows:

$\begin{matrix}{{b_{k}❘H_{1}} = {{y_{k} - {\frac{P_{k}}{{aP}_{k + 1}}y_{k + 1}}} = {{h_{k}\rho_{t}t_{k}} + n_{k} - {\frac{P_{k}}{{aP}_{k + 1}}\left( {{h_{k + 1}\rho_{t}t_{k + 1}} + n_{k + 1}} \right)} - \frac{\omega_{k + 1}\rho_{s}P_{k}}{a}}}} & (5)\end{matrix}$k∈{1, 2, . . . , L ₁−1}

Under the second condition, the expression for each symbol is asfollows:

$\begin{matrix}{{b_{k}❘H_{0}} = {n_{k} - {\frac{P_{k}}{{aP}_{k + 1}}n_{k + 1}} + \frac{\omega_{k + 1}P_{k}}{a}}} & (6)\end{matrix}$

It can be seen from the above formula that correlation noise existsbetween the adjacent symbols, and the correlation noise in formula (5)cannot be corrected by an ordinary noise whitening technique, and thecorrelation noise needs to be eliminated through step S402 to estimateh_(k)ρ_(t)t_(k)+n_(k).

In step S402, the target signal is estimated using the expression of thesymbol. The above formula (5) is expressed as follows:

$\begin{matrix}{u_{1} = {b_{1} = {{h_{1}\rho_{t}t_{1}} + n_{1} - {\frac{p_{1}}{{ap}_{2}}\left( {{h_{2}\rho_{t}t_{2}} + n_{2}} \right)} - \frac{\omega_{2}\rho_{s}p_{1}}{a}}}} & (7) \\\begin{matrix}{u_{k} =} & {{u_{k - 1} + {\frac{p_{1}}{a^{k - 1}p_{k}}b_{k}}} = {p_{1}{\sum\limits_{m = 1}^{k}\;\frac{b_{m}}{a^{m - 1}p_{m}}}}} \\{=} & {{h_{1}\rho_{t}t_{1}} + n_{1} - {\frac{p_{1}}{a^{k}p_{k + 1}}\left( {{h_{k + 1}\rho_{t}t_{k + 1}} + n_{k + 1}} \right)} -} \\ & {{\rho_{s}p_{1}{\sum\limits_{m = 1}^{k}\;\frac{\omega_{m + 1}}{a^{m}}}},{k \in \left\{ {2,L,{L_{1} - 1}} \right\}}}\end{matrix} & (8)\end{matrix}$

The estimated results may be obtained as follows:

$\begin{matrix}{z_{1} = {{\frac{1}{L_{1} - 1}{\sum\limits_{k = 1}^{L_{1} - 1}\; u_{k}}} = {{h_{1}\rho_{t}t_{1}} + n_{1} + ɛ_{1}}}} & (9) \\{z_{k} = {{\frac{a^{k - 1}p_{k}}{p_{1}}\left( {z_{1} - u_{k - 1}} \right)} = {{h_{k}\rho_{t}t_{k}} + n_{k} + ɛ_{k}}}} & (10)\end{matrix}$

Where ε_(k) in formula (10) is a residual signal generated in aninterference cancellation process by a BKIC module, and ε_(k) may bemodeled as a Gaussian distribution. For slow fading, (a→1) and thevariance of ε_(k) is small, so ε_(k) in z_(k) can be removed to obtainthe estimated h_(k)ρ_(t)t_(k)+n_(k), that is, the target signal withoutthe pilot signal is estimated.

In addition, in step S102, the carrier signal is subjected to BKICprocessing to obtain a target signal, and the target signal is subjectedto differential signal processing to obtain a target authenticationsignal.

In the present embodiment, the method of differential signal processingis as follows:

Under the first condition, the expression of differential signalprocessing is as follows:

$\begin{matrix}{{{r_{k}❘H_{1}} = {{\frac{1}{\rho_{t}^{2}}z_{k}z_{k + 1}^{*}} = {{a{h_{k}}^{2}t^{k}t_{k + 1}^{*}} + \Delta_{k}}}},{{iL} \leq k \leq {{iL} + L_{1} - 1}}} & (11)\end{matrix}$

Where Δ_(k) is the residual signal and may be approximately modeled as aGaussian random variable with a mean of zero and a variance of σ_(Δ)_(k) ².

Under the second condition, the expression of the differential signalprocessing is as follows:

$\begin{matrix}{{r_{k}❘H_{0}} = {{\frac{1}{\rho_{t}^{2}}\left( {n_{k} + ɛ_{k}} \right)\left( {n_{k + 1} + ɛ_{k + 1}} \right)^{*}} = \nabla_{k}}} & (12)\end{matrix}$

Where ∇_(k) is a zero-mean complex Gaussian random variable.

In the present embodiment, the physical layer blind authenticationmethod further includes: obtaining, by the receiver, a reference signalbased on the key and the pilot signal, performing differential signalprocessing on the reference signal to obtain a reference authenticationsignal, and calculating the correlation between the targetauthentication signal and the reference authentication to obtain a teststatistic (step S103).

In step S103, obtaining the reference signal based on the key and thepilot signal refers to obtaining the reference signal based on the keyand the pilot signal using the hash matrix. Thereby, the referencesignal is processed to obtain the reference authentication signal, andwhether the target authentication signal passes the authentication canbe determined according to the correlation between the referenceauthentication signal and the target authentication signal.

In step S103, the reference signal is subjected to differential signalprocessing to obtain the reference authentication signal, and thecorrelation between the target authentication signal and the referenceauthentication signal is calculated to obtain the test statistic, andthe next determination may be performed according to the value of thetest statistic.

In the present embodiment, the reference signal is subjected todifferential signal processing to obtain the reference authenticationsignal. The method of differential signal processing is the same as thedifferential processing method in the above step S102.

In the above step S102, the carrier signal received by the receiver mayinclude an authentication signal, and that the carrier signal includesthe authentication information is set as a first condition, and that thecarrier signal does not include the authentication signal is set as asecond condition.

At the receiver, for the carrier signal, blind known interferencecancellation (BKIC) processing and differential signal processing areperformed on the carrier signal to obtain a target authenticationsignal. At the receiver, a reference signal is obtained based on the keyand the pilot signal. The reference signal is subjected to differential(DP) signal processing to obtain a reference authentication signal. Therules for generating the reference signal by the hash matrix, the keyand the pilot signal at the receiver are the same as the rules forgenerating the authentication signal by the hash matrix, the key and thepilot signal at the transmitter. The reference authentication signal maybe regarded as the authentication signal under the first condition. Thetarget authentication signal may be regarded as the carrier signal underthe first condition. Thus, the first condition may be expressed asincluding the reference authentication signal in the targetauthentication signal; the second condition may be expressed as notincluding the reference authentication signal in the targetauthentication signal.

In the present embodiment, the physical layer blind authenticationmethod further includes comparing the test statistic with a prescribedthreshold to determine whether the carrier signal can pass theauthentication (step S104).

In step S104, if the test statistic is not less than the prescribedthreshold, it is determined that the carrier signal passes theauthentication; if the test statistic is less than the prescribedthreshold, it is determined that the carrier signal has not passed theauthentication.

In the present embodiment, if the test statistic is not less than theprescribed threshold, the carrier signal includes the referenceauthentication signal, that is, the carrier signal passes theauthentication; if the test statistic is less than the prescribedthreshold, the carrier signal does not include the referenceauthentication signal, that is, the carrier signal has not passed theauthentication.

In addition, in the present embodiment, the prescribed threshold isobtained by assuming the verification condition, and the first conditionand the second condition described above are the first condition H₁ andthe second condition H₀ of the assumption verification condition,respectively.

In the present embodiment, under the first condition H₁, the expressionof the test statistic is as follows:

$\begin{matrix}{{\tau_{i}❘H_{1}} = {{d_{i}^{H}r_{i}} = {{a{\sum\limits_{k = 1}^{L_{1} - 1}\;{{h_{{iL} + k}t_{{iL} + k}t_{{iL} + k + 1}}}^{2}}} + v_{i}}}} & (13)\end{matrix}$

Under the second condition H₀, the expression of the test statistic isas follows:

$\begin{matrix}{{\tau_{i}❘H_{0}} = {\phi_{i} = {\sum\limits_{k = 1}^{L_{1} - 1}\;{t_{k}^{*}t_{k + 1}\nabla_{k}}}}} & (14)\end{matrix}$

Where

$v_{i} = {\sum\limits_{k = 1}^{L_{1} - 1}\;{t_{k}^{*}t_{k + 1}\Delta_{k}}}$is a Gaussian random variable with a mean of zero and a variance ofσ_(v) _(i) ²=(L₁−1)σ_(Δ) ²σ_(p) ⁴. ϕ_(i) is a Gaussian random variablewith a mean of zero and a variance of σ_(ϕ) _(i) ²=(L₁−1)σ_(∇) ²σ_(p) ⁴.

In addition, the prescribed threshold τ_(i) ⁰ is determined by the falsealarm probability ε_(FA) associated with the (τ_(i)|H₀) distribution,and is expressed as follows:

$\begin{matrix}{\tau_{i}^{0} = {{\arg\mspace{14mu}{\min\limits_{\tau}\mspace{14mu}{\Phi\left( {\tau\text{/}\sigma_{\phi_{i}}} \right)}}} \geq {1 - ɛ_{FA}}}} & (15)\end{matrix}$

Where (τ_(i)|H₀) is the test statistic obtained under the secondcondition, that is, the statistical characteristic of the pilot signal.Thus, the prescribed threshold may be obtained based on the statisticalcharacteristic of the pilot signal and the preset upper limit of thefalse alarm probability.

In addition, in the present embodiment, if the identity of thetransmitter is authenticated, the authentication signal may be used asan extra pilot signal to recover the signal. Thereby, the performance ofsignal symbol recovery and the estimation performance of the channelresponse can be improved.

In addition, in the present embodiment, the authentication signal issuperimposed on the pilot signal, avoiding the adverse effect on theextraction of the conventional signal. Thereby, the signal tointerference plus noise ratio (SINR) of the receiver is prevented frombeing reduced.

In the present embodiment, the physical layer blind authenticationmethod of the wireless communication time-varying fading channel basedon the smoothing technique does not need to occupy extra signalbandwidth. In addition, at the receiver, when the information signal isextracted from the carrier signal, the authentication signal does notbecome the noise of the information signal, that is, the authenticationsignal does not affect the extraction of the information signal. Theauthentication signal does not affect the statistical characteristics ofthe noise at the receiver.

In the present embodiment, the physical layer blind authenticationmethod deals with the time-varying fading channel, and is more suitablefor a complex and variable wireless communication environment in anactual communication scenario. In addition, the authentication signal issuperimposed on the pilot signal. If the entire signal obtained bysuperimposing the authentication signal and the pilot is used as thepilot signal for channel estimation, the accuracy of the channelestimation can further be improved.

The embodiments disclose a physical layer blind authentication systemfor a wireless communication time-varying fading channel based on asmoothing technique. FIG. 5 is a schematic diagram illustrating signalprocessing modules of a transmitter in a physical layer blindauthentication system according to an embodiment of the presentdisclosure. FIG. 6 is a schematic diagram illustrating signal processingmodules of a receiver in a physical layer blind authentication systemaccording to an embodiment of the present disclosure.

In the present embodiment, as shown in FIG. 5, the physical layer blindauthentication system includes a transmitting device 20. Thetransmitting device 20 includes a first generation module 201, a secondgeneration module 202, and a synthesizing module 203.

In the present embodiment, as shown in FIG. 5, the first generationmodule 201 generates an authentication signal, that is, the key and thepilot signal generate an authentication signal via the first generationmodule 201. The first generation module 201 includes a hash matrix. Theauthentication signal is obtained based on the key and the pilot signalby using a hash matrix. The obtained authentication signal and the pilotsignal have the same signal length.

In the present embodiment, as shown in FIG. 5, the second generationmodule 202 generates a pilot portion of a carrier signal. That is, theauthentication signal is loaded onto the pilot signal by the secondgeneration module 202 to generate the pilot portion of the carriersignal. The expression of the pilot portion of the carrier signal isformula (1). In addition, the length of the pilot portion of the carriersignal is the signal length of the authentication signal or the signallength of the pilot signal.

In the present embodiment, as shown in FIG. 5, the synthesizing module203 generates a carrier signal, that is, the pilot portion and theinformation portion of the carrier signal are combined via thesynthesizing module 203 to generate a carrier signal. The informationportion of the carrier signal is an information signal.

In the present embodiment, the carrier signal is sent in blocksaccording to data blocks, each carrier signal block includes a pilotportion and an information portion, and the sum of the signal length ofthe authentication signal or the pilot signal and the signal length ofthe information signal is equal to the length of each carrier signalblock. In addition, the carrier signal is transmitted in blocks in theform of data blocks to facilitate operation of the data.

In the present embodiment, the carrier signal generated by thetransmitting device 20 at the transmitter reaches the receiving device30 at the receiver via a wireless channel. In addition, the wirelesschannel is the time-varying fading channel.

In the present embodiment, the physical layer blind authenticationsystem further includes a receiving device 30, and the receiving device30 includes a first processing module, a second processing module, and adetermining module.

In the present embodiment, the first processing module includes a blindknown interference cancellation (BKIC) module 301. After the carriersignal passes through the blind known interference cancellation (BKIC)module 301, the pilot signal in the carrier signal is cancelled.

In the present embodiment, the blind known interference cancellation(BKIC) module 301 employs the BKIC processing method of cancelling thepilot signal through the smoothing technique using adjacent symbols instep S102. The specific steps are shown in FIG. 4. The BKIC processingincludes determining an expression of each symbol under differentconditions (step S401) and estimating a target signal using theexpression of the symbol (step S402).

In the present embodiment, as shown in FIG. 6, the first processingmodule further includes a differential (DP) processing module 302. TheDP processing module 302 employs the differential signal processingmethod in step S102. The DP processing module 302 performs differentialsignal processing on the target signal to obtain a target authenticationsignal. Thereby, the effect of h_(k) in the target authentication signalis cancelled, i.e., the effect of the channel on the carrier signal iscancelled.

In the DP processing module 302, under the first condition, theexpression of the differential signal processing is formula (11), whereΔ_(k) is the residual signal, which may be approximately modeled as aGaussian random variable with a mean of zero and a variance of σ_(Δ)_(k) ². Under the second condition, the expression of the differentialsignal processing is formula (12), where ∇_(k) is a zero-mean complexGaussian random variable.

In the present embodiment, as shown in FIG. 6, the second processingmodule further includes a hash matrix processing module 303. A referencesignal is obtained based on the pilot signal and the key via the hashmatrix processing module 303. The hash matrix processing module 303employs the method of generating the reference signal in step S103, andthe hash matrix processing module 303 includes a hash matrix.

In the present embodiment, as shown in FIG. 6, the second processingmodule further includes a differential (DP) processing module 304. Thedifferential (DP) processing module 304 performs differential signalprocessing on the reference signal to obtain a reference authenticationsignal. The DP processing module 304 employs the differential signalprocessing method in step S103.

In the present embodiment, as shown in FIG. 6, the second processingmodule further includes an operation module 305. The operation module305 is configured to calculate a test statistic of the targetauthentication signal and the reference authentication signal. Thecalculation method used by the operation module 305 is the calculationmethod in step S103.

In the present embodiment, as shown in FIG. 6, the determining module306 determines whether the target authentication signal passes theauthentication by comparing the test statistic with the prescribedthreshold, that is, it is determined whether the carrier signal can passthe authentication.

In the present embodiment, the prescribed threshold in the determiningmodule 306 is obtained based on the statistical characteristics of thepilot signal and the preset upper limit of the false alarm probability.The calculation method of the prescribed threshold is the thresholdcalculation method in step S103.

The embodiments disclose a physical layer blind authentication device 50for a wireless communication time-varying fading channel based on asmoothing technique. FIG. 7 is a schematic structural diagram of aphysical layer blind authentication device according to an embodiment ofthe present disclosure. In the present embodiment, both the transmitterand the receiver include the authentication device 50 as shown in FIG.7.

In the present embodiment, as shown in FIG. 7, the authentication device50 includes a processor 501 and a memory 502. The processor 501 and thememory 502 are separately connected to the communication bus. The memory502 may be a high speed random access memory (RAM) or a non-volatilememory. It will be understood by those skilled in the art that thestructure of the authentication device 50 shown in FIG. 7 does notconstitute a limitation of the present disclosure. The structure may bea bus-shaped structure or a star-shaped structure, and may also includemore or fewer components than those shown in FIG. 7, or a combination ofsome components, or a different arrangement of components.

The processor 501 is a control center of the authentication device 50,and may be a central processing unit (CPU). The processor 501 connectsvarious parts of the entire authentication device 50 by using variousinterfaces and lines, and runs or executes software programs and/ormodules stored in the memory 502 as well as calls program codes storedin the memory 502 to perform the following operations.

The transmitter transmits a carrier signal to a wireless channel, wherethe carrier signal includes an authentication signal, a pilot signal andan information signal, the authentication signal is superimposed on thepilot signal, and the wireless channel is the time-varying fadingchannel (performed by the authentication device 50 at the transmitter).

The receiver receives the carrier signal, and performs blind knowninterference cancellation (BKIC) processing and differential signalprocessing on the carrier signal to obtain a target authenticationsignal, where in the BKIC processing, the pilot signal is cancelledthrough the smoothing technique by using adjacent symbols, the receiverobtains a reference signal based on the key and the pilot signal,performs differential signal processing on the reference signal toobtain a reference authentication signal, and calculates a correlationbetween the target authentication signal and the referenceauthentication signal to obtain a test statistic; and the test statisticis compared with a prescribed threshold to determine whether the carriersignal can pass authentication (performed by the authentication device50 at the receiver).

In the present embodiment, the processor 501 of the authenticationdevice 50 at the transmitter further performs the following operation:the carrier signal is transmitted in blocks in the form of data blocks.

In the present embodiment, the processor 501 of the authenticationdevice 50 at the transmitter further performs the following operation:in each carrier signal, the sum of the signal length of the pilot signaland the signal length of the information signal is equal to the signallength of the carrier signal.

In the present embodiment, the processor 501 of the authenticationdevice 50 at the receiver further performs the following operation: areference signal is obtained based on the key and the pilot signal usinga hash matrix.

In the present embodiment, the processor 501 of the authenticationdevice 50 at the receiver further performs the following operation: ifthe test statistic is not less than a prescribed threshold, the carriersignal passes the authentication.

In the present embodiment, the processor 501 of the authenticationdevice 50 at the receiver further performs the following operation: theprescribed threshold is obtained based on the statistical characteristicof the pilot signal and the preset upper limit of the false alarmprobability.

In the embodiments, it should be understood that the disclosed devicemay be implemented in other ways. For example, the device embodimentsdescribed above are merely illustrative. For example, the division ofthe units is only a logical function division, and another divisionmanner may be provided in actual implementation. For example, multipleunits or components may be combined or integrated into another system,or some features may be omitted or not implemented. In addition, thecoupling or direct coupling or communication connection shown ordiscussed may be an indirect coupling or communication connectionthrough some interfaces, devices or units, and may be electrical or thelike.

The units described as separate components may or may not be physicallyseparated, and the components displayed as units may or may not bephysical units, that is, may be located in one place, or may bedistributed to multiple network units. Some or all of the units may beselected according to actual needs to achieve the purpose of thesolution of an embodiment.

In addition, each functional unit in each embodiment may be integratedinto one processing unit, or each unit may exist physically separately,or two or more units may be integrated into one unit. The aboveintegrated unit may be implemented in the form of hardware or in theform of a software functional unit.

The integrated unit, if implemented in the form of a software functionalunit and sold or used as a standalone product, may be stored in acomputer readable memory. Based on such understanding, the technicalsolution of the present disclosure or the part contributing to theexisting art or all or part of the technical solution may be embodied inthe form of a software product. The computer software product is storedin a memory and includes several instructions for causing a computerdevice (which may be a personal computer, server or network device,etc.) to perform all or part of the steps of the methods described invarious embodiments of the present disclosure. The foregoing memoryincludes: a USB flash disk, a Read-Only Memory (ROM), a Random AccessMemory (RAM), a removable hard disk, a magnetic disk, or an opticaldisk, and the like, which may store program codes.

The embodiments disclose a computer readable storage medium. One ofordinary skill in the art will appreciate that all or part of thevarious steps of the above-described embodiments may be accomplished bya program (instruction) instructing the associated hardware. The program(instruction) may be stored in a computer readable memory (storagemedium), and the memory may include: a flash disk, a read-only memory(ROM), a random access memory (RAM), a magnetic disk or a CD, etc.

Although the present disclosure is described in detail in conjunctionwith the drawings and embodiments, it should be understood that theabove description is not intended to limit the present disclosure in anyform. Those skilled in the art may make variations and changes withoutdeparting from the spirit and scope of the present disclosure, and suchvariations and changes fall within the scope of the present disclosure.

What is claimed is:
 1. A physical layer blind authentication method fora time-varying fading channel based on a smoothing technique, being aphysical layer authentication method for wireless communication of awireless communication system having a transmitter and a receiver, andcomprising: transmitting, by the transmitter, a carrier signal to awireless channel, wherein the carrier signal comprises an authenticationsignal, a pilot signal, and an information signal, the authenticationsignal is superimposed on the pilot signal, and the wireless channel isthe time-varying fading channel; receiving, by the receiver, the carriersignal, and performing blind known interference cancellation (BKIC)processing and differential signal processing on the carrier signal toobtain a target authentication signal, wherein in the BKIC processing,the pilot signal is cancelled through the smoothing technique by usingadjacent symbols; obtaining, by the receiver, a reference signal basedon a key and the pilot signal, performing the differential signalprocessing on the reference signal to obtain a reference authenticationsignal, and calculating a correlation between the target authenticationsignal and the reference authentication signal to obtain a teststatistic; and comparing the test statistic with a prescribed thresholdto determine whether the carrier signal is capable of passingauthentication.
 2. The physical layer blind authentication methodaccording to claim 1, wherein the carrier signal is transmitted inblocks in a form of data blocks.
 3. The physical layer blindauthentication method according to claim 2, wherein a sum of a length ofthe pilot signal in each block of the carrier signal and a length of theinformation signal in each block of the carrier signal is equal to alength of the each block of the carrier signal.
 4. The physical layerblind authentication method according to claim 1, wherein the referencesignal is obtained based on the key and the pilot signal by using a hashmatrix.
 5. The physical layer blind authentication method according toclaim 1, wherein the carrier signal passes the authentication in a casewhere the test statistic is not less than the prescribed threshold. 6.The physical layer blind authentication method according to claim 1,wherein the prescribed threshold is obtained based on a statisticalcharacteristic of the pilot signal and a preset upper limit of a falsealarm probability.
 7. A non-transitory computer readable storage medium,which is configured to store at least one instruction which, whenexecuted by a processor, implements the physical layer blindauthentication method according to claim
 1. 8. A physical layer blindauthentication system for a time-varying fading channel based on asmoothing technique, comprising a transmitting device and a receivingdevice, wherein the transmitting device is configured to transmit acarrier signal to a wireless channel, wherein the carrier signalcomprises an authentication signal, a pilot signal and an informationsignal, the authentication signal is superimposed on the pilot signal,and the wireless channel is the time-varying fading channel; and whereinthe receiving device comprises: a first processing module, which isconfigured to receive the carrier signal and perform blind knowninterference cancellation (BKIC) processing and differential signalprocessing on the carrier signal to obtain a target authenticationsignal, wherein in the BKIC processing, the pilot signal is cancelledthrough the smoothing technique by using adjacent symbols; a secondprocessing module, which is configured to obtain a reference signalbased on a key and the pilot signal, perform the differential signalprocessing on the reference signal to obtain a reference authenticationsignal, and calculate a correlation between the target authenticationsignal and the reference authentication signal subjected to thedifferential signal processing to obtain a test statistic; and adetermining module, which is configured to compare the test statisticwith a prescribed threshold to determine whether the carrier signal iscapable of passing authentication.
 9. The physical layer blindauthentication system according to claim 8, wherein the secondprocessing module is configured to obtain the reference signal based onthe key and the pilot signal by using a hash matrix.
 10. The physicallayer blind authentication system according to claim 8, wherein in thedetermining module, the prescribed threshold is obtained based on astatistical characteristic of the pilot signal and a preset upper limitof a false alarm probability.